A computer simulation of LiKSO4

Molecular-dynamics computer-simulation of an ionic molecular solid LiKSO₄ has been carried out at 300 and 1000 K using the atom-atom potentials obtained from lattice dynamical studies. We observe hopping of lithium ions to interstitial positions which is related to reorientations of sulphate tetrahedra.     

矿井提升机下坠现象的解决措施

提出了矿井提升机下坠现象的解决措施,就此作了理论分析,并用计算机仿真出了速度跟随曲线。     

Effect of integrated extrusion–equal channel angular pressing temperature on microstructural characteristics of low carbon steel

Abstract

In the present research, a combined forward extrusion–equal channel angular pressing was developed and executed for the deformation of a plain carbon steel. In this method, two different deformation steps, including forward extrusion and equal channel angular pressing, take place successively in a single die. The deformation process was performed at different deformation start temperatures (800, 930 and 1100°C). Three-dimensional finite element simulation was used to predict the strain and temperature variations within the samples during deformation. With microstructural observations and the results of finite element simulation, the main grain refinement mechanisms were studied at different deformation temperatures. The results show that the forward extrusion–equal channel angular pressing is effective in refining the ferrite grains from an initial size of 32 μm to a final size of ～0·9 μm. The main mechanisms of grain refinement were considered to be strain assisted transformation, dynamic strain induced transformation and continuous dynamic recrystallisation, depending on the deformation temperature.     

露天矿生产车辆安排计划优化设计

本文结合露天矿车辆生产安排计划的特点,全面分析了车辆安排问题约束条件,构建了基于整数规划的线路车次安排数学模型。利用线性规划对电铲进行初始布点,实现对模型的合理简化,加速模型的求解。考虑到电铲利用率很难达到1,为提高模型最优解的实际应用的可行性,增加了车辆调度的弹性,设置了电铲的最大利用率。为保证电铲有一定的利用率,设置了电铲最小利用率。计算表明本模型具有较好的实用性和通用性。     

圆柱谐振腔式MPCVD装置中氢、氩微波等离子体分布规律的数值模拟

在使用简化的等离子体放电模型的基础上,模拟了圆柱谐振腔式微波等离子体沉积室中,不同金刚石膜生长条件下微波等离子体的分布状态。在模拟中,针对纳米金刚石的生长环境,就纯氩气反应气体中,不同的输入功率、不同气体压力条件下,沉积室中形成的等离子体分布的变化规律进行了模拟,将其与一般氢气气氛下的相应模拟结果相对比。模拟所获得的结果,对微波等离子体方法沉积金刚石膜的操作环境的优化,有着一定的指导意义。     

一种改进的气动弹性时域推进方法

针对气动弹性控制方程,结构项采用标准龙格库塔方法推进,广义气动力项采用时间上的插值技术,发展了一种在每一时间步内只用计算一次非定常气动力的近似四阶龙格库塔推进方法。通过计算非线性Bernoulli方程和某一超音速翼面的气动弹性响应,证明该方法的时间准确度远高于采用气动力冻结技术的四阶龙格库塔方法。其准确度与标准龙格库塔方法相差不大,而其调用非定常气动力求解器的次数仅为其四分之一,大大提高了气动弹性数值模拟的效率。对于一般的气动弹性响应而言,该时间推进方法只用保证每个周期内的时间步在20～30个左右就能满足较高的准确度要求。     

Minimum-Weight Design of Multipurpose Tie-Beam of Solid Cross-Section

The paper presents the minimum-weight design of an elastic, simply-supported member of solid cross-section that is to act as a tie for a part of its design life and as a beam for the rest, but not both at any given time. Upper bounds are prescribed on the longitudinal elongation under an axial tension and on the maximum deflection under a transverse concentrated load. The range of constraints is divided into regions of possible single-purpose minimum-weight designs. The effectiveness of optimization is judged against a prismatic bar having the same transverse stiffness.     

Simulating Retention in Gas–Liquid Chromatography: Benzene, Toluene, and Xylene Solutes

Accurate predictions of retention times, retention indices, and partition constants are a long sought-after goal for theoretical studies in chromatography. Although advances in computational chemistry have improved our understanding of molecular interactions, little attention has been focused on chromatography, let alone calculations of retention properties. Configurational-bias Monte Carlo simulations in the isobaric–isothermal Gibbs ensemble were used to investigate the partitioning of benzene, toluene, and the three xylene isomers between a squalane liquid phase and a helium vapor phase. The united-atom representation of the TraPPE (transferable potentials for phase equilibria) force field was used for all solutes and squalane. The Gibbs free energies of transfer and Kovats retention indices of the solutes were calculated directly from the partition constants (which were averaged over several independent simulations). While the calculated Kovats indices of benzene and toluene at T=403 K are significantly higher than their experimental counterparts, much better agreement is found for the xylene isomers at T=365 K.     

赖氨酸高产菌株的选育

赖氨酸作为一种重要的饲料用氨基酸,需求量一直在不断增长。传统的赖氯酸生产菌株都是多年来是经过多轮随机突变和筛选得到,而近年来随着基因重组技术的发展及对生物代谢过程的了解,人们已经能够通过基因重组技术,改变代谢途径,提高赖氨酸产量。目前有不少成功将野生菌株改造为高产菌株的案例,他们都可以作为合理设计代谢途径并结合各种组学进行微生物代谢途径改造的基础。本文主要描述通过代谢途径改造并结合高通量筛选技术,快速得到赖氨酸高产菌株的方法。     

Numerical simulation for rheological characteristics of alternating distribution of soft and hard rock layers

The difficulty of selecting appropriate rheological model and parameters for the alternating distribution of soft and hard rock layers was often encountered due to the unhomogeneity, discontinuity and anisotropy of rock mass. The Burgers and generalized Kelvin models were applied to the soft and hard rock respectively and the rheological parameters were obtained based on the method of optimum separation. By using the simulated code FLAC^3D, the stability of surrounding rocks of a certain underground plant was analyzed. The effect of surface load and weakening the parameters intensity of argillaceous and bioclastic interlayers between soft and hard rock on rheological behavior of layer composite rock mass was investigated. The results indicate that the rheological characteristics of soft and hard rock layer in composite rock mass can be described well with above two rheological models.